Are any of you shutting down all manufacturing machines when a thunderstorm approaches? My company is/has been doing this forever and tell me it's to protect the machines. I could see doing it to protect boards in the machines (except we have battery backup on the ovens, so they'll come out anyway). Just wondering, is this a common practice and is it necessary?

Been getting wacked by lightning for twenty years in this business. (three times yesterday as a matter of fact) We have never shut down in anticipation that we are going to get hit. I have lost one motherboard in all of these years that cost about $2300 to replace not including lost revenue from being down for 2 days. However, if we shut down everytime a storm came in the revenue lost would be in the millions. We usually turn the machines back on figure out where the placements / process left off and finish up. There are power conditioners and surge protectors that will protect your machines from power anomalies

We have surge suppressors on every machine we have as well as suppression on the mains coming in the building. The power in the area has always had too much noise and we did have losses due to surges during storms and such. Three phase surge suppressors are a cheap investment.

We don't shut the machines down, we keep them working, however,sometimes the AC supply gets down because of a storm so we have a Forced shut down, as someone said, if we shut equipment down on every storm that represents $$ millions $$. The bad thing about blackouts is when we turn machines on, sometimes we have some damaged controllers either in ovens or P&P machines, but that's because of the variation we have on 3 phase supply when power is coming back. I guess we should consider Suppressors

if your company would loose millions by shutting down during every storm, then you should invest 100k$ in a standby generator big enough to feed the whole plant. We did this and the generator paid itself off after a couple of blackouts. Plus, when you see a bad storm coming, you can switch over to the generator before the storm hits, thus preventing damage from lightning strikes